Add message confirmation

[moisses89]

Description

Adds confirm_message for tx-service mode.
This new command let the user add confirmation for a created message in the transaction service.

Closes #346

Other changes

• sign_message for EIP191 is receiving now the message to sign as input instead of parameter, previous implementation had issues with quotes and blank spaces, also this new approach let the user paste longer messages.
• refactor submit signatures to reuse the function sign_transaction, cleaning at this way duplicated code.

[coveralls]

coverage: 86.772% (-0.2%) from 86.934%
when pulling 949e84f on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling e1c6100 on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling 53e6bff on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling b8b048e on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling 734f8d5 on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling 64bcea1 on add_message_confirmation
into 88ca917 on main.

[coveralls]

coverage: 87.279% (+0.3%) from 86.934%
when pulling 0e4d426 on add_message_confirmation
into 88ca917 on main.